The present invention relates to an improvement in the construction and fabrication of copper cookware.
While copper cookware is preferred for its superior heat transfer capabilities, the food contacting portions must be covered with an inert coating that prevents the leaching of copper and copper oxides into food, as well as the staining of the cooking surface. Traditionally, tin coatings have been used. However, these wear off over time. Further, tin is a soft metal which scratches easily.
Another approach is to clad copper with stainless steel so that after forming the food contacting surface is steel. While stainless steel is relatively durable and inert, it scratches easily. Far more significant, stainless steel is a poor conductor of heat, so the cooking performance is not as good as tinned copper, even when the stainless steel is relatively thin. While such clad metal constructions deploy some layers of aluminum between the copper and stainless steel, the steel is still a limitation to heat transfer. Further, such laminates are complicated to fabricate and expensive, having many layers that must be metallurgically bonded in the cladding process. For this reason, depending on the sheet cladding process, the copper core is not always continuous, and can be very thin, with holes or perforations though which the aluminum layers are extruded through to bond to each other encapsulating the copper.
It is therefore a first object of the present invention to provide copper cookware with improved durability for long life and easy maintenance without sacrificing the thermal performance.
It is also an object of the invention to provide copper cookware that requires less or no cooking oil to prevent food from sticking, as well as making cleaning and maintenance easier for the consumer.